<p>The mass transfer in nanopores is understood respectively from the multiscale flow regime and the nanoscale non-continuum flow regime according to the size of the nanopore. If no interfacial slippage occurs, the mass flow rate through the nanopore is normally far smaller than the classical Hagen–Poiseuille equation calculation especially for small nanopores owing to the fluid-pore wall interaction which results in the significant effects of the viscosity enhancement and the non-continuum property of the very thin adhering layer in the nanopore. If the interfacial slippage occurs, in the multiscale flow regime, the adhering layer-pore wall interfacial slippage is advantageous over the adhering layer-continuum fluid interfacial slippage especially for small nanopores because of generating much greater flow rates through the nanopore. A hydrophobic nanopore wall is thus preferential. In the nanoscale non-continuum flow regime, the wall slippage more easily occurs, and its effect is determined by both the power loss on the nanopore and the intrinsic parameter of the nanopore.</p>